Which of the following conditions is an absolute contraindication for exercise during pregnancy?

In the context of pregnancy and exercise, an absolute contraindication is a condition that poses a significant risk and completely prohibits a woman from engaging in physical activity. The history of premature labor is one such condition. This can indicate an underlying issue that makes the uterus more susceptible to contractions and can lead to an increased risk of premature birth. As such, exercising could potentially provoke a repeat of these contractions, leading to complications for both the mother and baby.

Gestational diabetes, high blood pressure, and excessive weight gain, while they may present challenges during pregnancy, are often managed through exercise and lifestyle modifications under appropriate medical guidance. In many cases, women with these conditions can engage in safe exercise programs tailored to their specific needs, which are monitored and adapted as necessary.

Thus, the history of premature labor stands out as an absolute contraindication against exercise during pregnancy due to the high risks involved.